This invention relates to a tubular belt conveyor wherein the circulating belt is rolled up into a tube, and materials, loaded on the belt are transferred while being wrapped, and in particular, to a tubular belt conveyor which is designed to prevent the belt from being twisted during travelling between a pair of rollers.
There is conventionally known a tubular belt conveyor which is adapted to transfer granulated materials or bulk materials in the open air. One example is disclosed in my earlier Pat. No. 4,402,395. The tubular belt conveyor is so designed that an endless belt except for both end portions thereof is rolled up into a tube so as to carry the granulated materials or bulk materials in a wrapped state in order to prevent these loaded materials from getting wet in the rain, being blown away or falling out of the belt.
FIGS. 7 to 10 illustrate an example of such a conventional tubular belt conveyor as mentioned above. Reference numeral 1 shows an endless belt made, for example, of rubber. This endless belt 1 is so manufactured in advance that, when released, it will spontaneously roll up into a tube due to its elasticity with both fringe portion 1, and 1" being overlapped one upon another. However, portions of the endless belt each engaging with the upper driving roller 2 and the lower driven roller 3 are unfolded flat. Other portions of the endless belt 1 which are rolled up into a tube are sustained by a number of supporting frames 4 disposed at a predetermined interval (1 m to 2 m). Each of the supporting frames 4 is provided, as shown in FIG. 10 in the upper and lower portions thereof, with an upper belt passageway 4a and a lower belt passageway 4b, and also with a plurality of belt-retaining rollers 5 circumferentially disposed at regular intervals around each of the belt passageways 4a and 4b. Each of the belt-retaining rollers 5 is fixed to the supporting frames 4 through a bracket 5a.
At the forward side of the driven roller 3 as well as the backward side of the driving roller 2 are disposed, as shown in FIGS. 8 & 9, a plurality of curling-extending frames 6 for rolling or unfolding the endless belt 1 in stepwise fashion. Each of the supporting frames 6 is provided in the upper and lower portions thereof with an upper belt passageway 6a and a lower belt passageway 6b, and also with a plurality of belt-deforming rollers 7 disposed in each of the belt passageways 6a and 6b in such a manner that the plurality of belt-deforming rollers 7 form a segmental circular shape. In this case, a pair of the belt-deforming rollers 7 disposed at both sides of the belt passageways 6a and 6b are so adjusted in mounting angle that those disposed in the supporting frame 6 nearer to the driven roller 3 (or driving roller 2) are less inclined.
The forward-moving belt 1a which is once unfolded flat upon turning around the lower driven roller 3 is gradually rolled up to be finally formed into a tubular shape due to the elastic tendency to restore its original tubular shape, and also due to the presence of plural sets of the deforming rollers 7, each arranged to form a segmental circular shape.
While the belt 1a is being rolled up as mentioned above, materials "m" to be conveyed are dropped onto the belt 1a from a hopper 8 and wrapped by the belt 1a . The belt la, now formed into a tubular shape with both fringe portions 1, and 1" thereof being overlapped one upon the other, passes through the upper passageway 4a of each supporting frame 4. Upon passing through the last supporting frame 4 which is located at the most forward site, the belt 1a is gradually unfolded flat by the upper deforming rollers 7 mounted on the rolling-unfolding frame 6 disposed near the driving roll 2, and turned around the driving roller 2, thereby dropping the material "m" loaded on the belt 1a into a receiving cylinder 9.
Then, the forward-moving belt la is turned into a backward-moving belt 1b which is again gradually rolled up by passing through the lower deforming rollers 7 mounted on the rolling-unfolding frame 6. Upon passing through a sequence of the lower passageways 4b of supporting frames 4, the belt 1b is again unfolded flat in front of the driven roller 3 by the lower deforming rollers 7 of the rolling-unfolding frames 6 disposed near the driven roller 3, and then turned around the driven roller 3 to repeat the forward movement as described above.
Meanwhile, it is frequently required to install a tubular belt conveyor having a length of as long as several hundred meters or more from a loading site to an unloading site, with the line of the tubular belt conveyor being bent upward, downward, leftward or rightward in accordance with the features of topography. Under these conditions, the running tubular belt is liable to be twisted around its axis 10 due to the following reasons: (i) A difference in contacting condition of the tubular belt to a retaining roller between that disposed at the inner circumference and that at the outer circumference at a curved portion of the tubular belt; (ii) A difference in frictional resistance of the tubular belt to the retaining rollers mounted on each of the supporting frames due to the characteristics or uneven distribution of materials carried on the pipe-like belt, or due to an uneven physical feature of the belt; and (iii) A slipping between the retaining rollers and the belt due to an adhesion of water to the rollers or the belt. As a result, the loaded materials are more likely to fall out, or the flattened portions of the belt engaging with the driving roller 2 or driven roller 3 are more likely to be dislocated relative to these rollers 2 and 3, thereby inhibiting these rollers from normally rotating.
In order to correct these malfunctions of the tubular belt conveyor, it is necessary to stop the operation of the conveyor in order to adjust the belt, or to incline either some of the retaining rollers mounted on the supporting frame or a roller disposed separate from the retaining rollers relative to the axis of the tubular belt thereby to adjust the belt (for example, Japanese unexamined patent disclosure No. 57-137206). However, these countermeasures are nothing but a sort of symptomatic therapy. Moreover, these adjusting operations, which are conducted whenever the twisting of the belt occurs, are not only troublesome, but also ineffective in coping with a long length of three-dimensionally curved tubular belt.